JPS61259716A - System for operational control of electroosmotic dehydrator - Google Patents

Abstract

PURPOSE:To obtain a dehydrated cake with constant water content in spite of the variation in the properties of sludge, by measuring the electric resistance of sludge by a current detection means and operating water content on the basis of the measured value to control voltage to be applied. CONSTITUTION:From the measured values of the currents supplied to the electrode segments positioned correspondingly to a mechanical press dehydration region I and an electroosmotic dehydration region II and the output voltage of a power source apparatus 9, the electric specific resistance of sludge at each point in a sludge feed passage 6 including an electroosmotic dehydration region is operated. Water content is operated from a preliminarily obtained experimental result by an operator 19 to be outputted to a controller 20. The controller 20 compares the operated value with an objective set value and, if the water content of a dehydrated cake is high, the voltage of a power source is raised and an electroosmotic current is increased to enhance dehydration capacity. Contrarily, if low, the voltage applied to an electrode is lowered to suppress current.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to an operation control system for an electroosmotic dehydrator that dehydrates sludge generated in a sewage treatment plant to form a cake.

[Prior art and its problems]

An electric immersion (sWA*) apparatus that continuously processes sludge by applying electroosmosis to the above-mentioned sludge, etc., has been conventionally implemented with a configuration as shown in FIG. 4. In FIG. 4, 1 is a rotating drum on the anode side with an electrode 2 arranged on its outer periphery, and 3 is a press that also serves as an electrode member on the cathode side and stretched between sprockets facing the circumferential area of the rotating drum 1. The belt 4 is a filter cloth stretched over the circumferential surface of the press belt 3. /j^・+1.
LC: There is an OLL claw 19 in the l, a slurry conveying passage 6 is formed in the area where the rotating drum 1 and the filter belt 4 face each other, and a slurry conveying passage 6 is formed on the entrance side of the passage 6. A supply hopper 7 is installed, and these constitute the main body of the electroosmotic dewatering apparatus. Note that the passage 6 is formed so that the passage width gradually narrows from the inlet side to the outlet side. Further, a belt conveyor 8 for supplying slurry is provided on the population side facing the hopper 7, and a positive terminal of a DC power supply 9 is connected to the rotary drum 1 facing the press belt 3 on the ground side. are connected via a power supply brush and a current collector slip ring. In addition, 10 is a dish for the filtration light installed below the filter belt 4 in the main body of the dehydrator, 11 is a collection container for the dehydrated cake, and 12 is a scraper for peeling off and scraping off the dehydrated cake adhering to the filter belt 4. be. When the drive motor 5 is operated with this configuration and a voltage is applied between the electrode 2 and the press belt 3 from the power supply 9, the slurry is supplied from the hopper 7 to the slurry transport path 6 via the slurry supply belt conveyor 8. When the slurry iA as a dewatered product is supplied, the slurry is sandwiched between the rotary drum 1 and the press belt 3 and conveyed by the belt a in the direction of the arrow P, and during this conveyance process, it is subjected to mechanical squeezing force. It comes to be affected by the electric field formed between the opposing electrodes. As a result, dehydration of the slurry A progresses mainly in the region near the entrance side of the passageway due to mechanical squeezing force, and dehydration progresses in the region behind it due to electroosmotic action caused by the electric field. In the electroosmotic dewatering area, the water contained in the sludge is positively charged and flows toward the cathode press belt 3, where it is discharged to this electrode member and passes through the filter belt 4 to be separated and dehydrated from the sludge, and is then inside the passage. The filtrate water and the filtrate water dehydrated from the compression dewatering section in the front area drip onto the dish 10 and are drained out of the system. In this case, the amount of filtrate transferred (dehydration amount) due to electroosmosis is proportional to the current flowing through the mud. On the other hand, the sludge remaining in the conveyance passage 6 is concentrated and caked by the above-mentioned dewatering operation, becomes a dehydrated cake B with a low water content, is sent out from the outlet of the passage Ia6, and is peeled off from the filter belt 4 by the scraper 12. It is collected in the collection container 11. Note that the dehydrated cake produced by dehydrating sludge generated at a sewage treatment plant is usually incinerated or composted to be recycled as fertilizer. By the way, the properties of the sludge generated in the above-mentioned sewage treatment plants and the like, especially its concentration, are not always constant and vary depending on the situation. Therefore, when this sludge is dehydrated using an electroosmotic dehydrator, if the operating conditions are kept constant, the water content of the dehydrated cake will change as the properties of the sludge change. On the other hand, it is desirable that the water content of the dewatered cake of sludge produced through the electroosmotic dehydrator is approximately constant in consideration of subsequent processing. However, if the electroosmotic dehydrator continues to operate under certain conditions, if the sludge concentration becomes lower than normal, the water content of the dehydrated cake will increase due to insufficient dehydration during the dehydration process. If the sludge concentration is high, it will cause problems when the dehydrated cake is then incinerated, for example, and if the sludge concentration is high, it will result in excessive dewatering. :*m6 Tsugu'n7TIT'F
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bMk, resulting in uneconomical driving. From this point of view, in order to operate the electroosmotic dehydrator efficiently and to obtain a dehydrated cake with a stable desired moisture content regardless of changes in the properties of the slurry, it is necessary to measure and monitor the moisture content of the dehydrated cake while the dehydrator is operating. However, when this water content deviates from the target set value, the electroosmotic dehydrator is activated by using the deviation between the measured water content of the dehydrated cake and the target set value as a feed batter signal to change the voltage applied between the electrodes. It is necessary to control the operation. On the other hand, infrared moisture content meters have long been well known as a general means of measuring the moisture content of substances, but when this infrared moisture content meter is used for measuring dehydrated cakes in an electroosmotic dehydrator, The following problems arise. In other words, in an electroosmotic dehydrator, heat is generated due to the passage of electric current during the dehydration process, and a large amount of steam is generated from the dehydrated cake after the dehydration process. For this purpose, the dehydrated cake is measured using the infrared moisture content meter at a point on the outlet side of the dehydrator.
. When you try to do this, the steam generated from the dehydrated cake
□It becomes extremely difficult to measure the water content correctly because it absorbs the measurement light and becomes a disturbance factor in the measurement. In addition, the dehydrated cake discharged from the electroosmotic dehydrator has a lump-like surface with uneven surfaces, so in order to measure it with an infrared moisture content meter, the surface of the dehydrated cake must be leveled to a smooth surface. Formatting and operations are required. However, this operation is troublesome, which makes it even more difficult to apply an infrared moisture content meter.

[Purpose of the invention]

This invention has been made in consideration of the above points, and it is an object of the present invention to detect the energization state of the in-machine power supply circuit of an electroosmotic dehydrator without directly measuring the moisture content of a dehydrated cake with the above-mentioned infrared moisture content meter or the like. Operation of an electro-osmotic dewatering machine that allows the moisture content of the dehydrated cake to be accurately grasped indirectly from G, and based on this, optimal operation control can be performed in response to changes in the properties of the slurry. The purpose is to provide a control method.

[Key points of the invention]

In order to achieve the above object, the present invention is equipped with a current detection means in the power supply circuit to the electrode in the machine, and the slurry is detected at each point including the electroosmotic dehydration area in the slurry transport passage through the current detection means. The electrical resistance of the dehydrated cake is measured and the moisture content of the dehydrated cake is calculated from this measured value, and the deviation between this calculated value and the target set value of the dehydrated cake moisture content is used as a feedback signal to control the applied voltage between the electrodes. This is how it was done. In other words, according to the knowledge obtained from the slurry dehydration experiment conducted using the electroosmotic dehydrator mentioned above, the mud inside the machine! ! i When the water content of the slurry, which was 80% in the compression dewatering area near the population side in the conveyance passage, is subjected to the electroosmotic dehydration process and is reduced to 70% during this period, the electricity of the slurry decreases to 70%. It has been confirmed that the electrical resistivity of the slurry increases as electroosmotic dehydration progresses, such as increasing by 2.3 to 3 times depending on the properties of the slurry. An example of the characteristics showing the relationship between the in-machine dehydration section and the electrical resistance of the slurry in this case is shown in Fig. 3, where the section numerators, n, and I [l in the figure are mechanical as will be described later. It is also possible to show the compressed dehydration area, the electrolytic osmosis dehydration area, and the dehydrated cake conveyance area. Therefore, within the range where the properties of the slurry do not change significantly, the electrical resistance of the slurry at each point including the electroosmotic dewatering area in the slurry transport passage is measured, and based on this, the electrical resistance of the slurry confirmed in the above experiment is used. By contrasting and calculating the characteristics of the relationship between and the moisture content of the dehydrated cake, the moisture content of the dehydrated cake obtained in the current operation can be indirectly grasped. Furthermore, changes in the electrical resistance of the slurry during the dehydration process can be determined by detecting the current flowing through the electrodes corresponding to each point in the slurry transport passage, and by calculating the ratio of this current measurement value to the voltage applied to the electrode at the measurement point. It can be easily determined by adding and calculating constants determined by the dimensions of the slurry conveying path and the measurement position. By comparing the moisture content of the dehydrated cake indirectly determined in this way with the desired moisture content target set value, and controlling the applied electrode to the electrode using the deviation as a feedback signal, the To obtain a dehydrated cake with constant moisture content ++ ILL
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The operation of the electroosmotic dehydrator can be optimally controlled so that

Embodiments of the Invention FIGS. 1 and 2 each show operation control system diagrams of different embodiments of the invention, and members corresponding to those in FIG. 4 are given the same reference numerals. First, in the embodiment shown in FIG. 1, the anode side electrode 2 installed on the rotating drum 10 circumference 1 consists of a large number of electrode segments 2a arranged and divided on the drum circumference, and between each electrode segment 2a. are insulated and isolated by an insulator 2b. On the other hand, each of the electrode segments 2a is interconnected via a lead wire 14 in a one-to-one correspondence with each segment 13a of a divided current collecting slip ring 13 installed on the drum side. Further, a split-type power supply brush indicated by reference numeral 15 is disposed at a predetermined position on the same side facing the slip ring 13, and lead wires 16 drawn out individually from the brush segments 15a of the power supply brush are shown in detail. It is connected to the positive side terminal of the source device 9 via a switch of the IIT selection selection device 17, which will be described later, and constitutes a power supply circuit. The above-mentioned energization selection switch device 17 is used to specify the width of the electroosmotic dehydration region in the slurry transport passage 6 by an external command, and selects the electrode segment 2a corresponding to the command to control the power supply circuit. By turning on the switch contact, the specified width of the electroosmotic dewatering region in the slurry conveying passage 6 is adjusted. In the illustrated example, for each electrode segment 2a of the anode side electrode 2, the switch contact of the energization selection switch W17 inserted in the circuit corresponding to the electrode segment position d to h among the electrode segments indicated by the symbols a w h is turned on. , shows a state in which operation is performed with the switch contacts corresponding to the remaining electrode segment positions turned off and the electroosmotic dehydration region specified in the range dh. As a result, inside the slurry conveying passage 6, dewatering is performed by mechanical squeezing force in the area near the inlet side, which is represented by the section ■, with the electrode segment marked d as the border, and the electrodes d-h, which are shown by the section ■, are dehydrated. Electroosmotic dehydration will take place in the area of the segment area. In addition, the exit side section 2 behind the electrode segment with the same symbol represents the conveyance area of the dehydrated cake. Although the press belt 3 and the rotating drum 1 are moved in the direction of the arrow by the drive operation of the drive morph 5 shown in FIG. The electroosmotic dehydration area will be formed at the same location. For such a configuration, a current detector 18 interposed in the lead wire 16 of the power supply circuit that individually connects each brush segment of the power supply brush 15 and the power supply, and arithmetic units and control units indicated by numerals 19 and 20 are provided. The operation control system of the electroosmotic dehydrator according to the present invention is configured by the device. Here, a selection signal for the energized electrode segment is sent to the calculator 19 from the energization selection switch device 17, and an electrode current flows from each current detector 18 to the electrode segment 2a corresponding to each position of the slurry transport path 6. Further, the output voltage of the power supply device 9 is inputted from the voltage detector 21 . Based on these input information, the calculator 19 calculates the result of the electrode segment with the code a' corresponding to the dehydration category ■!
current (the contact of the energization selection switch device 17 is turned on for a short time in the pole segment a for current measurement), and the sign d-h located corresponding to the electroosmotic dehydration region of the segment
The electrical resistivity of the slurry at each point in the slurry transport passage 6 including the electroosmotic dehydration region is calculated from the measured value of the current flowing through each electrode segment and the output voltage of the power supply device 9, and further a summary is obtained. After calculating the moisture content of the dehydrated cake by comparing the characteristic data of the relationship between the resistance of the slurry and the moisture content of the dehydrated cake written in the calculator 19 based on the experimental results with the above-mentioned calculated value, feed rate signal
It is output to the controller 20 as a turn signal X. On the other hand, the target setting value y of the dehydrated cake moisture content is given to the controller 20,
The output voltage of the power supply device 9 is controlled using the deviation from the feed bank signal X as the control signal 2. That is, if the calculated value of the water content of the dehydrated cake is higher than the target setting value, the source voltage is increased to increase the electroosmotic current and improve the dewatering ability. On the other hand, due to changes in the properties of the slurry, such as an increase in the concentration of the supplied slurry, the derobing route 4. 47+/Mr. Iezaki Ui Naokami 117〈If excessive dehydration occurs, the voltage applied to the electrodes should be lowered to suppress the current and avoid consuming excess power; operation control. I do. In addition, the electrodes corresponding to each point on the slurry transport path □
As a method of detecting the current, instead of using multiple current detectors as shown in the figure, one current detector is installed in a common power supply circuit, and each current detector is sequentially detected by switching the switch contact with the energization selection switch device. It is also possible to implement a method of detecting the current flowing through the electrode segment, or a method of detecting the current using a separate measurement power source. By measuring the slurry resistance at each point along the slurry conveyance path and controlling the power supply voltage in this way, the moisture content of the dehydrated cake being carried out from the electroosmotic dehydrator can be directly measured using an infrared moisture content meter, etc. By using the electrode current, which can be easily measured within the system, as a detection signal, the electroosmotic dehydrator can be optimally controlled so that the moisture content detected by dehydration is always constant. Next, FIG. 2 shows another embodiment of the present invention. In the embodiment shown in FIG. 2, instead of the energization selection switch device 17 in the embodiment shown in FIG. The brush is configured as a movable brush having a width that spans the nopling segment, and is moved over the slip ring 13 by the brush moving mechanism 22 to select the electrode segment 1-2a to be energized, and therefore to select the electrode segment 1-2a to be energized, and therefore to select the electrode segment 1-2a to be energized, and therefore to select the electrode segment 1-2a to be energized. For such a configuration, a current detector 18 is interposed in the lead wire 14 interconnecting each electrode segment 2a and the slip ring 13 individually. The current detector 18, the arithmetic unit 19, and the controller 20 constitute an operation control system.Here, the output signal of the current detector 18 and the position at which the movement position of the feed brush 15 described above is detected. The output signal of the detector 23 and the output signal of the power supply voltage detector 21 are given to the calculator 19, and based on these input signals, the calculator 19 calculates the moisture content of the dehydrated cake in the same manner as in the previous embodiment. The moisture content determined by the calculator 19 is output as a feedback signal X to the controller 20, and the controller 20 controls the output voltage of the power supply device 9.In addition, each of the above embodiments uses the rotating drum shown in FIG. Although a continuous treatment type electroosmotic dehydrator in combination with a press belt has been exemplified, it goes without saying that the present invention can also be implemented in the same manner with a belt-type electrode member on the anode side instead of a rotating drum. [Effects] As described above, according to the present invention, a current detection means is provided in the power supply circuit to the electrodes in the machine, and the current detection means is used to detect the mud 3 [at each point including the electroosmotic dehydration area in the conveyance path]. The electrical resistance of the slurry is measured and the water content of the dehydrated cake is calculated from this measured value, and the deviation between this calculated value and the target set value of the water content of the dehydrated cake is used as a feedback signal to apply the applied voltage between the electrodes. By controlling the water content of the dehydrated cake, the slurry conveyance path can be easily measured from the power supply circuit in the system, without directly measuring the water content of the dehydrated cake using an infrared water content meter, etc., which is difficult to apply to electroosmotic dehydrators. Using the current flowing through the electrodes corresponding to each point as the detected value, the electroosmotic dehydrator can be optimally controlled to maintain a constant water content of the dehydrated cake and to significantly reduce power consumption.

[Brief explanation of drawings]

Figures 1 and 2 are operational control system diagrams of an electroosmotic dehydrator according to an embodiment of the present invention, and Figure 3 is a characteristic diagram showing changes in electrical resistance of slurry as the electroosmotic dehydration process progresses. , FIG. 4 is a block diagram of a continuous processing type electroosmotic dehydrator. In the figure, 2: electrode member on the anode side, 2a: electrode segment, 3: press belt that also serves as the electrode member on the cathode side, 4: filter belt, 6: slurry conveyance path, 9: power supply device, 18: current detector , 19: water content calculator, 2o: controller, A: slurry, B: dehydrated cake. , (Jfi person) t-, 22 Yamaguchi mutual figure 3

Claims (1)

[Claims] 1) A slurry transport path is formed between an anode side electrode member and a cathode side electrode member that are arranged to face each other, and a voltage is applied between the opposing electrodes from a DC power supply device. In an electroosmotic dewatering machine, the water contained in the slurry supplied to the slurry conveyance passage in the system is separated and dehydrated outside the system by electroosmotic dehydration to turn the slurry into a dehydrated cake. A detection means is provided, and the electric resistance of the slurry is measured at each point including the electroosmotic dehydration area in the slurry transport passage through the current detection means, and the water content of the dehydrated cake is calculated from the measured value. An operation control method for an electroosmotic dehydrator, characterized in that the applied voltage applied between the electrodes is controlled using the deviation between the calculated value and the target set value of the water content of the dehydrated cake as a feedback signal. 2) In the operation control method described in claim 1, the electrode on the anode side is composed of a row of electrode segments divided along the slurry transport path, and each electrode segment is connected to a power source via a current detection means. An operation control method for an electro-osmotic dehydrator, characterized in that the current flowing through a power supply circuit that connects the individual parts is detected.